1. Field of the Invention
The present invention relates generally to electrical interconnection structures, and more particularly, concerns an interconnection structure capable of providing connections for diverse signals among a plurality of units.
2. Background of the Invention
There are several distinct types of imaging systems utilized in contemporary nuclear medicine. One type may employ gamma scintillation cameras (GSCs), so-called “position sensitive” continuous-area detectors, or simply, nuclear detectors. An exemplary GSC is a single photon emission computed tomography (SPECT) scanner. Another type of imaging system involves computed tomography (“CT”) of X-ray imaging. In contrast, magnetic resonance imaging (MRI) visualizes the inside of living organisms by making use of the relaxation properties of excited hydrogen nuclei in water placed in a powerful, uniform magnetic field.
Gamma rays are an energetic form of electromagnetic radiation produced by radioactive decay or other nuclear or subatomic processes such as electron-positron annihilation. Gamma rays form the highest-energy end of the electromagnetic spectrum. They are often defined to begin at an energy of 10 keV, a frequency of 2.42 EHz, or a wavelength of 124 pm, although electromagnetic radiation from around 10 keV to several hundred keV is also referred to as hard X-rays.
Gamma scintillation cameras, GSCs, are primarily used to measure gamma events produced by very low-level radioactive materials (called radionuclides or radio-pharmaceuticals) that have been ingested by, or injected into, a patient. The signals from the GSCs are used to generate images of the anatomy of organs, bones or tissues of the body and/or to determine whether an organ is functioning properly. The radiopharmaceuticals are specially formulated to collect temporarily in a certain part of the body to be studied, such as the patient's heart or brain. Once the radio-pharmaceuticals reach the intended organ, they emit gamma rays that are then detected and measured by the GSCs. Nuclear detectors perform spectroscopy and event X/Y positioning by processing signals from a constellation of Photo-multiplier Tubes (PMTs). One current series of detectors contains 59 PMTs.
To guard against the deleterious effects of stray X-rays blinding the scintillation crystal and the PMTs and possibly damaging the associated electronics, a GSC has a lead enclosure, i.e., tub, to block the stray X-rays. Furthermore, because the scintillation crystal emits faint amounts of light upon scintillation, the interior of the GSC must be shielded from ambient light that would blind the photosensors in the GSC used to measure the scintillation light emissions.
Owing to the large number of interconnections between PMT preamplifiers and an acquisition electronics system, portions of the acquisition electronics system have typically been packaged inside the tub. Because these connections generate heat, a significant amount of heat accumulates in the tub, detrimentally affecting the GSC's reliability. Likewise, the connections involve numerous printed circuit boards (PCBs) and cables, which must be disassembled to access a PMT needing replacement, making the GSC hard to service. Similarly, because the detectors need to be built in test stands, disassembled and then reassembled in the tubs, this arrangement of the connections compounds the effort needed to manufacture the GSCs.
While this arrangement has been functional, reliability, serviceability and manufacturability would all benefit if the electronics could be relocated outside of the tub. For these electronics to be placed outside the tub, an electrical penetration of the tub must support all of the PMT interconnections, including high and low voltage power supply voltages, balanced (differential pair) RF signals, and a serial data stream for analog-to-digital converters.